1. Field of the Invention
The present invention relates to a vibration generating apparatus which can be built into a mobile phone, touch panel, or other device, more particularly relates to a vibration generating apparatus which exhibits a vibration tactile haptic effects of instantaneous vibration.
2. Description of the Related Art
A vibration generating apparatus giving the vibration tactile haptic effects disclosed in Japanese Patent Publication (A) No. 2008-521597 employs a resonant forced vibration system. A signal generator generates an excitation use actuator signal of a first frequency the same as the natural frequency of the resonance actuator and excites the resonance actuator in the resonance state so as to sharply increase the acceleration instantaneously. After this, the signal generator generates a damping use actuator signal of a second frequency shifted from the first frequency by a 180 degree phase (waveform inverted) and dampens the resonance actuator to cause instantaneously damping.
As related art, there is Japanese Patent Publication (A) No. 2008-521597 (0033, FIG. 1)
The above resonance actuator is made to operate in a resonance mode using a forced vibration frequency the same as its natural frequency (resonant frequency), so while instantaneous excitation is easy in the excitation process which rapidly increases the acceleration, in the damping process for damping the once high acceleration resonance actuator, since the resonance actuator will have quite of a bit of variation in natural frequency for each specimen, even if the phase of the damping use actuator signal completely shifts by 180 degrees from the excitation use actuator signal, in reality there is no guarantee of a complete 180 degree shift with respect to the phase of the vibration and displacement of the resonance actuator. Due to this advanced phase difference or retarded phase difference which occurs unavoidably due to variations in the natural frequency, depending on the timing of the end of application of the damping use actuator signal, incomplete stopping of the mechanical vibrator or restart after stopping will be induced, so the free damping period remains longer until entering the insensitive zone and the sharpness of the damping becomes poor.